Currently balloon drivers (Virtio,XEN, HyperV, VMWare, ...)
inflate and deflate the guest memory size but there is no
way to know how much the memory size is changed by them.

A common use of the ballooning is to emulate [1]
hot plug and hot unplug - due to the complexity of the later.
Hotplug has a notifier and one can also check the updated
memory size.

To improve this add InflatedTotal and InflatedFree
to /proc/meminfo and implement a balloon notifier.

Amount of inflated memory can be used:
 - si_meminfo(..) users can improve calculations
 - adjust cache/buffer sizes
 - adjust object/connection limits
 - as a hint for the oom a killer
 - by user space software that monitors memory pressure

Patches for the other balloon drivers will be done next.

Alexander Atanasov (4):
  Make place for common balloon code
  Enable balloon drivers to report inflated memory
  Display inflated memory to users
  drivers: virtio: balloon - update inflated memory

 Documentation/filesystems/proc.rst            |  6 +++
 MAINTAINERS                                   |  4 +-
 arch/powerpc/platforms/pseries/cmm.c          |  2 +-
 drivers/misc/vmw_balloon.c                    |  2 +-
 drivers/virtio/virtio_balloon.c               |  7 +++-
 fs/proc/meminfo.c                             | 10 +++++
 .../linux/{balloon_compaction.h => balloon.h} | 30 ++++++++++----
 mm/Makefile                                   |  2 +-
 mm/{balloon_compaction.c => balloon.c}        | 40 +++++++++++++++++--
 mm/migrate.c                                  |  1 -
 mm/vmscan.c                                   |  1 -
 11 files changed, 87 insertions(+), 18 deletions(-)
 rename include/linux/{balloon_compaction.h => balloon.h} (86%)
 rename mm/{balloon_compaction.c => balloon.c} (88%)

v2:
 - reworked from simple /proc/meminfo addition
v3:
 - added missed EXPORT_SYMBOLS
Reported-by: kernel test robot <lkp@intel.com>
 - instead of balloon_common.h just use balloon.h (yes, naming is hard)
 - cleaned up balloon.h - remove from files that do not use it and
   remove externs from function declarations

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: pv-drivers@vmware.com
Cc: Jason Wang <jasowang@redhat.com>
Cc: virtualization@lists.linux-foundation.org
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: linux-hyperv@vger.kernel.org
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: xen-devel@lists.xenproject.org

base-commit: 1c23f9e627a7b412978b4e852793c5e3c3efc555
-- 
2.31.1